An energy capacitor system (ECS) is an electrical power storage system consisting of capacitors, parallel monitors and a current pump, and has been already introduced in literature (e.g., "A Basic Study on Power Storage Capacitor Systems", Denki Gakkai Ronbunshi, Vol. 115-B, No. 5, May 1995, pp. 504-510). In the ECS, electrical energy is stored in the plural capacitors connected in series. A charging control circuit known as a parallel monitor is connected across the terminals of each capacitor. During charging, the parallel monitor bypasses the charging current around the capacitor when the terminal voltage has reached a preset voltage, and thus prevents further charging of the capacitor.
As a result, all the capacitors connected in series are uniformly charged up to the preset voltage. In consequence, it is possible to derive almost the full storage capacity of the capacitor assemblage.
Today, manufacture of a large-sized energy capacitor system using thousands of electrical double layer capacitors is being discussed. Whenever a few capacitors of such a large-sized energy capacitor system are at fault, if the operation is stopped and the defective capacitors are replaced, the efficiency of the operation will not be high. If the operation is continued without replacing the defective capacitors, and if the whole system is serviced at regular intervals of time, then the efficiency of the operation of the system will be enhanced. This will save the cost of servicing the system.
It is an object of the present invention to provide a power supply that acts to store electrical energy in capacitors and has a function of shorting out defective capacitors.